Make it illegal to place blocks inside of the hitbox of entities

[IntegratedQuantum]

Requires #88

This only matters for other entities, the player itself is already covered.

[ikabod-kee]

Seeing as the duplicate #628 was fixed, I think I'll close this. Now we'll be 4 issues away from surpassing java.

[IntegratedQuantum]

#628 was only closed because it was a duplicate of this. This problem still happens, and will continue to happen for a while.
It might be debatable, whether this should be on the surpass java milestone, but that's a different question.